By reporting unauthorized border crossings, the observers hope to help outnumbered border officers, Donnelly said. He is a Republican candidate for the 8th congressional district, which covers much of the desert area north of Imperial County.

The border-watching exercise was in part a reaction to the caravan of Central Americans who traveled through Mexico to enter the U.S. at the border between San Diego and Tijuana, said Donnelly, a former assemblyman.

A group of Minutemen and border security supporters gather together, what they call a muster, at the Pio Pico RV Resort & Campground, southwest of Jamul, before heading to the U.S. - Mexican border to observe and report any signs of illegal immigration to the U.S. Border Patrol on Saturday, May 5, 2018.

(Hayne Palmour IV)

It was also meant as a warning to Gov. Jerry Brown, who signed the California Values Act, which limits law enforcement in the state from certain kinds of cooperation with federal immigration officials. The law has been criticized as an effort to make California a sanctuary for unauthorized immigrants.

“My hope is that we will reignite the (Minuteman) movement and that people will again be aiding (border agents) for longer periods of time, longer musters,” Donnelly said.

The camouflage-dressed volunteers, wearing boots, bringing backpacks and other wilderness gear, were instructed on safety such as avoiding rattlesnakes before heading out from Pio Pico campground.

Volunteers were told to avoid confrontations with border crossers if possible, and to help those in distress.

“There is no animus toward those who are crossing desperate, you know, to escape oppression,” Donnelly said. “But at the same time, among those people come through wolves, people who mean harm people like Luis Bracamontes, who was just recently sentenced to death here in California for executing two sheriff's deputies up in Sacramento.”

While expressing sympathy for plight of border crossers, Donnelly and others blasted Brown, who they said has violated his oath of office.

“This is not about waving American flags,” Donnelly said. “This is about actually securing the border and sending a message to the political authorities, to Jerry Brown.

“I dare Jerry Brown to come down and arrest me, because you might get arrested down here for being a tyrant, for being a traitor, for aiding and abetting illegal aliens and harboring them in violation of federal law, which is the supreme law of the land when it comes to immigration.”

Lisa Collins of Orange County said she had been a member of the Minuteman group since 2005, when illegal immigration surged.

“There were so many illegals that were coming across the border, and I'm one that believes you can't complain about a subject unless you're willing to do something about it,” Collins said.

Supporter Ben Bergquam said he was there to show solidarity with the group, although not taking part in the border watch. He is co-founder and spokeman for the Fight Sanctuary State Movement.

“I represent the angel parents who've lost their loved ones to criminal illegal aliens that are protected by the lawless politicians like Jerry Brown,” Berqguam said.

The group is preparing to launch a statewide initiative to repeal California’s “sanctuary state” legislation, Bergquam said.